1. Field of the Invention
The present invention relates to a method of mounting a wafer on a printed wiring substrate.
2. Description of Background Art
A conventional method of mounting a wafer such as an IC or the like on a printed wiring substrate is structured as shown in FIG. 7. The structure is made such that a wiring circuit 101 is formed on a top surface of a printed wiring substrate 100, and a wafer 102 is provided with electrodes 103 and 103 on a top surface or a side surface thereof. Further, the wafer 102 is first mounted on the printed wiring substrate 100 as shown in FIG. 7(1), the electrodes 103 and 103 of the wafer 102 next connected to the wiring circuit 101 of the printed wiring substrate 100 by wires 104 and 104 as shown in FIG. 7(2), and the portion of the wires 104 and 104 are finally sealed 105 by a resin as shown in FIG. 7(3).
However, in the case of the conventional method mentioned above, only one side surface of the wafer can be used.
Further, as a different mounting method from that mentioned above, as shown in FIG. 8, there is a mounting method by forming a rewiring circuit 107 on one surface of a wafer 106, forming a solder bump 108 in the rewiring circuit, and bonding the solder bump 108 to the wiring circuit 101 of the printed wiring substrate 100. In this case, a thermal stress relaxing post is omitted in the drawing.
In the case of the mounting method mentioned above, as is different from the mounting method first mentioned, piled plural wafers can be mounted. In other words, it is possible to use both upper and lower surfaces. Accordingly, in the case of the mounting method mentioned above, the structure is made such that a printed wiring sheet 109 as shown in FIG. 9 is adhered to a top surface of the wafer 106 in a lowest stage which is directly bonded to the printed wiring substrate 100, a solder bump 112 formed in a rewiring circuit 111 in a wafer 110 in an upper stage side is bonded thereto, and the printed wiring sheet 109 and the wiring circuit 101 of the printed wiring substrate 100 are connected by a wire 113.
However, in accordance with the mounting method mentioned above, it is necessary to prepare the printed wiring sheet 109 in addition to the wafer, and extra labor and time are required. Further, when adhering the printed wiring sheet 109 to the wafer, it is necessary to align positions of both the elements, so that workability is deteriorated. Further, labor for connecting by the wire 113 one by one is required.